Synchronous coupling of defects and a heteroatom-doped carbon constraint layer on cobalt sulfides toward boosted oxide electrolysis activities for highly energy-efficient micro-zinc-air batteries.

Abstract

The sluggish kinetics of oxygen electrocatalysis reactions on cathodes significantly suppresses the energy efficiency of zinc-air batteries (ZABs). Herein, by coupling in situ generated CoS nanoparticles rich in cobalt vacancies (VCo) with a dual-heteroatom-doped layered carbon framework, a hybrid Co-based catalyst (Co1-xS@N/S-C) is designed and synthesized from Co-MOF precursor. Experimental analyses, together with density functional theory (DFT)-based calculations, demonstrate that the facilitated ion diffusion enabled by the introduced VCo, together with the enhanced electron transport benefiting from the well-designed dual-heteroatom-doped laminated carbon framework, synergistically boost the bifunctional electrocatalytic activity of Co1-xS@N/S-C (ΔE = 0.76 V), which is much superior to that of CoS@N/S-C without VCo (ΔE = 0.89 V), CoS without VCo (ΔE = 1.23 V), and the dual-heteroatom-doped laminated carbon framework. As expected, the further assembled ZAB employing Co1-xS@N/S-C as the cathode electrocatalyst exhibits enhanced energy efficiency in terms of better cycling stability (510 cycles/170 hours) and a higher specific capacity (807 mA h g-1). Finally, a flexible/stretched solid state micro-ZAB (F/SmZAB) with Co1-xS@N/S-C as the cathode electrocatalyst and a wave-shaped GaIn-Ni-based liquid metal as the electronic circuit is further designed, which can display excellent electrical properties and long elongation. This work provides a new defect and structure coupling strategy for boosting the oxide electrolysis activities of Co-based catalysts. Furthermore, F/SmZAB represents a promising solution for a compatible micropower source in wearable microelectronics.